Ammonium cations, exemplified by benzyl trimethyl ammonium (BTMA), have long been used for hydroxide exchange membranes (HEMs), establishing the cation standard for HEMs. Recently, the quaternary phosphonium cation benzyl tris(2,4,6-trimethoxyphenyl) phosphonium (TPQPBn) was attached to a polymer backbone to effectively improve the alkaline stability, hydroxide conductivity and solubility of HEMs. TPQPBn based HEMs showed better alkaline stability than those based on BTMA analogs. However, still further improvements would be beneficial.